The present invention relates to an electromechanical time switch intended to provide time-of-day control of lighting, heating, air-conditioning, pumps, motors or general electrical circuits. They are commonly used in residential, commercial, industrial and agricultural facilities.
Such an electromechanical time switch is an electric motor driven clock mechanism which operates an electrical switch to automatically activate electrical devices or circuits at pre-selected times and intervals each day of the week (24 hour time switch) and/or on a different schedule each day of the week (7 day time switch). The electric motor driving the clock mechanism may be an alternating current synchronous motor or a direct current stepping motor pulsed by a quartz crystal oscillator. Synchronous motors are most widely used because of their low cost and greater accuracy. The switch may be Single Pole Single Throw, Single Pole Double Throw, Double Pole Single Throw, or Double Pole Double Throw.
In the prior art, a separate model of electromechanical time switch was required for each voltage (120 V, 240 V, 277 V, etc.) (V in this application refers to Volts AC). Because the electric motors operate reliably only within a narrow voltage range (100 V to 132 V is typical for a nominal 120 V motor.) This increases the inventory of manufacturers, distributors, wholesalers, and retailers as well as necessitating that the purchaser know the voltage at which the time switch will be operated.
It is an object of the invention to provide a multi-voltage time switch which offers economies in manufacturing and distribution as well as convenience to the installation service person.
According to the present invention, a compact 120 V synchronous or quartz motor driven time switch clock unit is employed which is mounted upon a printed circuit board which contains resistors and jumpers which enable the installer to select the proper voltage (120 V, 208/240 V, or 277 V) for the application. Furthermore, the compact time switch activates one or more relays with higher switch ratings to perform the load switching. Other voltages, or more than three voltage selections can be provided with additional resistors and jumpers.